1. Field of the Invention
The present invention relates to a laser processing technique for processing a workpiece by irradiating laser light on the workpiece.
2. Description of the Related Art
In a process for manufacturing apparatus or device, e.g., a disk drive apparatus, a spindle motor or a bearing device, laser processing in which various precision parts used in the apparatus or device are processed by irradiating laser light thereon is performed. To be more specific, the laser processing includes laser welding in which two precision parts are welded together by laser light, laser forming in which the posture of a precision part is adjusted by laser light, laser trimming in which the surface of a precision part is cut by laser light, and laser marking in which letters or symbols are carved on the surface of a precision part by laser light.
Conventionally, laser processing has been performed in such a way that laser light is irradiated while a nitrogen gas is injected toward a workpiece. This is to prevent a workpiece (e.g., precision part to be processed) from being oxidized by the irradiation of laser light.
As the laser light is irradiated on a target processing point of the workpiece, however, the temperature of the target processing point is increased and fumes (or metal vapors) are generated from the target processing point. This poses a problem in that the fumes adhere to the surface of the workpiece near the target processing point. Particularly, if the laser light is irradiated while injecting a nitrogen gas toward the workpiece as in the conventional case, the fumes generated from the target processing point are injected toward the surface of the workpiece together with the nitrogen gas. This worsens the problem of fume adherence.
FIG. 20 is a micrograph showing the surface of a workpiece near a target processing point after a sleeve and a cap employed in a bearing device have been laser-welded according to a conventional method. It can be seen in FIG. 20 that multiple white spots generated by the adherence of fumes exist on the surface of the workpiece that has undergone the conventional laser welding.
With the conventional method, fumes adhere to the surface of the workpiece during the laser processing as mentioned above. Therefore, a process (a cleaning operation) for wiping away the fumes from the surface of the workpiece needs to be carried out after the laser processing. Another problem is that the laser processing is not applicable to the hard-to-clean internal regions of precision parts.